Method and device for controlling a powertrain

ABSTRACT

A method controlling a powertrain fitted in an automobile and including an electric motor including a rotor and stator, the method including: regulation of currents of the rotor and the stator via control signals from the electric motor, wherein the currents and control signals are expressed in a rotating coordinate system and include a plurality of axes, the control signals resulting from a first transformation including a change of variable that enables dynamic decoupling between the control signals, along each of the axes of the plurality of axes; saturation of the control signals resulting from the first transformation to satisfy constraints of a battery fitted in the automobile and connected to the electric motor; and blockage of at least some of the current reference values of the regulation if the control signals are saturated.

The technical field of the invention is the control of electric motors,and in particular the control of the electric motors of wound rotorsynchronous type.

An electric motor of wound rotor synchronous type comprises a fixed partcalled stator and a moving part called rotor. The stator comprises threewindings offset by 120° and powered by alternating current. The rotorcomprises one winding powered by direct current.

The currents of the phases of the stator depend on the resistances andinductances of the rotor and of the stator as well as on the mutualinductance between the rotor and the stator.

The control of such a system requires account to be taken of the controlsaturation phenomena, due in particular to the voltage limits of thebattery.

The document U.S. Pat. No. 3,851,234 discloses a method for avoiding themagnetic saturation by reducing the speed of the motor or the torquesupplied.

The document U.S. Pat. No. 5,015,937 discloses the control of asynchronous machine with wound rotor in open loop mode with data tablesfor avoiding saturations.

Finally, the document U.S. Pat. No. 6,181,091 discloses the control of asynchronous machine with permanent magnet in which the saturation isavoided by modifying the operation of the PWM (Pulse Width Modulation)ensuring the voltages on each branch of the motor.

However, there is no provision in the prior art of a saturation makingit possible to maintain a dynamic decoupling of the controls.

One aim of the present invention is to improve the quality of regulationof an electric motor of wound rotor synchronous type via a saturationwhich maintains the decoupling between the control of the rotor and thatof the stator.

According to one implementation, there is defined a method forcontrolling a power train installed in a motor vehicle and comprising anelectric motor provided with a rotor and a stator, comprising:

-   -   regulation of the rotor and stator currents via control signals        for the electric motor, said currents and said control signals        being expressed in a revolving reference frame, for example the        Park reference frame, and comprising a plurality of axes, said        control signals being derived from a first transformation        comprising a change of variable allowing for dynamic decoupling        between the control signals along each of the axes of said        plurality of axes;    -   saturation of said control signals obtained from said first        transformation to satisfy the constraints associated with a        battery installed in the motor vehicle and connected to the        electric motor; and    -   blocking of at least some of the regulation current setpoints if        the control signals are saturated.

The control method has the advantage of a total decoupling between therotor current setpoints and the stator current setpoints allowing forimproved wheel torque setpoint tracking. This decoupling is maintainedduring saturation since the saturation is applied to the decoupledcontrol signals expressed according to the first transformation.Furthermore, it is possible to ensure a total control of the currents byblocking the current setpoints.

In other words, the saturation strategy ensures stability by virtue ofthe peak-clipping performed in the decoupled space. Furthermore, sincethe current setpoints are recalculated in the event of saturation, thismakes it possible to reach stable current values as close as possible tothe real setpoints even if the setpoints are unreachable. Therecalculated current setpoints are therefore the maximum reachablecurrent setpoints.

According to one feature, the method also comprises a secondtransformation comprising a change of variable that is the reverse ofsaid change of variable allowing for dynamic decoupling so as to expressthe control signals after saturation in said revolving reference framewithout a change of variable.

Thus, it is then possible to express the control signals directly in thePark reference frame for example.

According to an additional feature, the method also comprises acommunication of information relating to the saturation of the controlsignals and the blocking of the regulation current setpoints isperformed on the basis of this information.

It is thus possible to block the current setpoints so as to avoid thesaturation of the control signals.

According to another implementation, there is defined a system forcontrolling a power train installed in a motor vehicle and comprising anelectric motor provided with a rotor and a stator, comprising:

-   -   means for regulating the rotor and stator currents using control        signals for the electric motor, said currents and said control        signals being expressed in a revolving reference frame, for        example, the Park reference frame, and comprising a plurality of        axes, said control signals being obtained from a first        transformation comprising a change of variable allowing for the        dynamic decoupling of the control signals along each of the axes        of said plurality of axes;    -   means for saturating said control signals obtained from said        first transformation to satisfy the constraints associated with        a battery installed in the motor vehicle and connected to the        electric motor; and    -   a blocking means configured to perform the blocking of at least        some of the current setpoints of the regulation means if the        control signals are saturated.

According to one feature, the system also comprises a means forcomputing a second transformation comprising a change of variable thatis the reverse of said change of variable allowing for the dynamicdecoupling so as to express the control signals after saturation in saidrevolving reference frame without a change of variable.

According to an additional feature, the system also comprises means forcommunicating information relating to the saturation of the controlsignals and the blocking means blocks the current setpoints of theregulation means on the basis of this information.

Other aims, features and advantages will become apparent on reading thefollowing description, given purely as a nonlimiting example and withreference to the appended drawings in which:

FIG. 1 illustrates a method for controlling an electric power train, and

FIG. 2 illustrates a device for controlling an electric power train.

To assure the regulation of a power train comprising a synchronous motorcomprising a stator and a rotor and installed in a vehicle, an inverteris used that makes it possible to control the voltage of the statorphases and a chopper for controlling the rotor voltage. These twodevices are powered by a battery installed in the vehicle.

A Park reference frame is also used, which makes it possible to expressthe electrical quantities in a revolving reference frame for examplelinked to the rotor in the case of a synchronous motor. This referenceframe comprises three axes: d, q and f. The axes d and q are associatedwith the stator and the axis f is associated with the rotor. The controlsignals for the electric motor V_(d), V_(q), V_(f) and the currentsetpoints applied I_(d) I_(q) I_(f) correspond to the components of acontrol signal and of a current respectively along the axes: d, q, f.

In the Park reference frame, a power train comprising a synchronousmotor is governed by the following equations:

$\begin{matrix}{{V_{d} = {{R_{s} \cdot I_{d}} + {L_{d} \cdot \frac{I_{d}}{t}} + {M_{f} \cdot \frac{I_{f}}{t}} - {\omega_{r} \cdot L_{q} \cdot I_{q}}}}{V_{q} = {{R_{s} \cdot I_{q}} + {L_{q} \cdot \frac{I_{q}}{t}} + {\omega_{r}\left( {{L_{d} \cdot I_{d}} + {M_{f} \cdot I_{f}}} \right)}}}{V_{f} = {{R_{f} \cdot I_{f}} + {L_{f} \cdot \frac{I_{f}}{t}} + {\alpha \cdot M_{f} \cdot \frac{I_{d}}{t}}}}} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$

with:

-   -   L_(d): Armature equivalent inductance on the axis d.    -   L_(q): Armature equivalent inductance on the axis q.    -   L_(f): Rotor inductance.    -   R_(s): Equivalent resistance of stator windings.    -   R_(f): Resistance of the rotor.    -   M_(f): Mutual inductance between the stator and the rotor.    -   I_(d): Current on the axis d.    -   I_(q): Current on the axis q.    -   I_(f): Current on the axis f.    -   ω_(r): Rotation speed.    -   V_(d): Electric motor control signal on axis d.    -   V_(q): Electric motor control signal on axis q.    -   V_(f): Electric motor control signal on axis f.    -   a: A coefficient, for example equal to 1.5.

The values L_(d), L_(q), L_(f), R_(s), R_(f) and M_(f) are, for example,known from prior measurements.

The main difficulties controlling this type of system lie in the dynamiccoupling between the axes d and f, and in the voltage constraints of thepower supply battery installed in the vehicle.

To avoid the dynamic coupling between the axes d and f, a change ofvariables is provided: ({tilde over (V)}_(d), {tilde over (V)}_(q),{tilde over (V)}_(f))−S(V_(d), V_(q), V_(f)), using the followingequation:

$\begin{matrix}{{V_{d} = {{\overset{\sim}{V}}_{d} - {\frac{M_{f}}{L_{f}} \cdot \left( {{R_{f} \cdot I_{f}} + {\frac{a \cdot M_{f}}{L_{d}} \cdot \left( {{\omega_{r} \cdot L_{q} \cdot I_{q}} - {R_{s} \cdot I_{d}}} \right)} - \overset{\sim}{V_{f}}} \right)}}}\mspace{20mu} {V_{q} = {\overset{\sim}{V}}_{q}}\mspace{20mu} {V_{f} = {{\overset{\sim}{V}}_{f} + {\frac{a \cdot M_{f}}{L_{d}} \cdot {\overset{\sim}{V}}_{d}}}}} & \left( {{Eq}.\mspace{14mu} 2} \right)\end{matrix}$

The system to be controlled can then be represented by the followingequations:

$\begin{matrix}{{{\overset{\sim}{V}}_{d} = {{R_{s} \cdot I_{d}} + {L_{d} \cdot \frac{I_{d}}{t}} - {\omega_{r} \cdot L_{q} \cdot I_{q}}}}{{\overset{\sim}{V}}_{q} = {{R_{s} \cdot I_{q}} + {L_{q} \cdot \frac{q}{dt}} + {\omega_{r} \cdot \left( {{L_{d} \cdot I_{d}} + {M_{f} \cdot I_{f}}} \right)}}}{{\overset{\sim}{V}}_{f} = {{R_{f} \cdot I_{f}} + {L_{f} \cdot \frac{I_{f}}{t}} - {\frac{3M_{f}}{2L_{d}} \cdot \left( {{R_{s} \cdot I_{d}} - {\omega_{r} \cdot L_{q} \cdot I_{q}}} \right)}}}} & \left( {{Eq}.\mspace{14mu} 3} \right)\end{matrix}$

with:

-   -   {tilde over (V)}_(d): Stator decoupled voltage on the axis d.    -   {tilde over (V)}_(q): Stator voltage on the axis q.    -   {tilde over (V)}_(f): Decoupled voltage of the rotor.

As can be seen, there is no change of variable on the axis q which doesnot exhibit any dynamic coupling. The dynamic coupling is between theaxes d and f, hence the new controls decoupled on these two axes.

With regard to the voltage constraints of the power supply battery withthe respective use of an inverter and of a chopper, they are describedby the following equation 4:

$\begin{matrix}{{V_{d}^{2} + V_{q}^{2}} \leq {\frac{V_{bat}^{2}}{3} - V_{bat}} \leq V_{f} \leq V_{bat}} & \left( {{Eq}.\mspace{14mu} 4} \right)\end{matrix}$

With Vbat being the voltage of the battery.

FIG. 1 proposes a control method which makes it possible to calculatecontrol signals {tilde over (V)}_(d), {tilde over (V)}_(q), {tilde over(V)}_(f) for controlling the currents I_(d), I_(q) and I_(f) so as tosatisfy the torque demands on the wheel while resolving the maindifficulties mentioned above which lie in the dynamic coupling betweenthe axes d and f, and in the voltage constraints of the power supplybattery installed in the vehicle.

The method comprises a step 1. This step comprises a step of acquisitionof the current setpoints (see step 2), namely the following setpoints:

-   -   if: the stator current setpoint on the axis d.    -   if: the stator current setpoint on the axis q.    -   if: the rotor current setpoint on the axis f.

The current setpoints are directly linked to the engine torque demand.

The step 1 also comprises a step of blocking of the current setpointsI_(d) ^(ref), I_(q) ^(ref), I_(f) ^(ref) which will be described laterin the description. The current setpoints then become: I_(d) ^(ref)_sat,I_(q) ^(ref)_sat, I_(f) ^(ref)_sat.

The step 1 is followed by a step 2 in which the rotor and statorcurrents (I_(d), I_(q), I_(f)) are regulated with control signals({tilde over (V)}_(d), {tilde over (V)}_(q), {tilde over (V)}_(f)) forthe electric motor for the rotor and stator currents (I_(d), I_(q),I_(f)) to reach the current setpoint values I_(d) ^(ref)_sat, I_(q)^(ref)_sat, I_(f) ^(ref)_sat. For this, the regulator is synthesized inthe following form:

{tilde over (V)} _(d) =K _(d)·(I _(d) ^(ref)_sat−I _(d))+K _(id)·∫(I_(d) ^(ref)_sat−I _(d))

{tilde over (V)} _(q) =K _(q)·(I _(q) ^(ref)_sat−I _(q))+K _(iq)·∫(I_(q) ^(ref)_sat−I _(q))

{tilde over (V)} _(f) =K _(f)·(I _(f) ^(ref)_sat−I _(f))+K _(if)·∫(I_(f) ^(ref)_sat−I _(f))   (Eq. 5)

With K_(d), K_(q), K_(f), K_(id), K_(iq), K_(if) being the settingparameters.

The currents and the control signals of equation 5 (Eq. 5) are expressedin the Park reference frame.

The control signals are obtained from a first transformation comprisinga change of variable described by equation 2 (Eq. 2). Thus, theregulator makes it possible to determine a voltage along the axis d({tilde over (V)}_(d)) dependent on the current derivatives only byvirtue of the component of the current along the axis d(I_(d)).Similarly, the voltage along the axis q ({tilde over (V)}_(q)) and therotor voltage ({tilde over (V)}_(f)) along the axis f depend on thecurrent derivatives only by the component of the current along the axisq(I_(q)) and along the axis f(I_(f)) respectively. The dynamic couplingsbetween the axes d, q, f are therefore eliminated at the regulatorlevel. There is a static coupling which is compensated by the integralcomponent of the regulator.

The regulation step also comprises a step of measuring of the currentsI_(d), I_(q) and I_(f), followed by a filtering and a scaling of thesemeasurements. The regulation step also comprises a step of acquisitionof the setting parameters.

The step 2 is followed by a step 3 of saturation of the control signals({tilde over (V)}_(d), {tilde over (V)}_(q), {tilde over (V)}_(f)).

To saturate the control signals calculated in step 2, it would bepossible, according to a first, non-optimal solution, to calculate thecontrols V_(d), V_(q), V_(f) actually applied to the system in the Parkreference frame without the change of variable of the equation 2 andthen to saturate these controls to satisfy the constraints associatedwith the battery in the Park reference frame in accordance with equation4 (Eq. 4). That said, this first solution is not optimal because, byperforming the saturation in the Park reference frame without the changeof variable of equation 2, the dynamic decoupling is lost. In practice,in the case of saturation in the Park reference frame, the value of thecontrols (V_(d), V_(q), V_(f)) will be modified by clipping withoutnecessarily retaining the decoupling which was present for the controls{tilde over (V)}_(d), {tilde over (V)}_(q), {tilde over (V)}_(f)obtained from the change of variable. This can result in risks of lossof control of the motor.

In the method illustrated in FIG. 1, in step 3, a saturation of thecontrols calculated in the step 2 is performed according to a moreadvantageous second solution which comprises a saturation of thecontrols {tilde over (V)}_(d), {tilde over (V)}_(q), {tilde over(V)}_(f) obtained from the first transformation comprising the change ofvariable using equation 2 (Eq. 2).

For this,

$A_{f} = {{R_{f} \cdot I_{f}} + {\frac{a \cdot M_{f}}{L_{d}} \cdot \left( {{\omega_{r} \cdot L_{q} \cdot I_{q}} - {R_{s} \cdot I_{d}}} \right)}}$

is deposited, and equations 2 and 4 (Eq. 2 and Eq. 4) are combined; thefollowing inequalities are thus obtained:

${\left( {{\overset{\sim}{V}}_{d} + {\frac{M_{f}}{L_{f}} \cdot {\overset{\sim}{V}}_{f}} - {\frac{M_{f}}{L_{f}} \cdot A_{f}}} \right)^{2} + {\overset{\sim}{V}}_{q}^{2}} \leq \frac{V_{bat}^{2}}{3}$${{and}\left( {{\overset{\sim}{V}}_{f} + {\frac{a \cdot M_{f}}{L_{d}} \cdot {\overset{\sim}{V}}_{d}}} \right)}^{2} \leq V_{bat}^{2}$

The following inequalities are therefore deduced therefrom:

${- V_{bat}} \leq {{\overset{\sim}{V}}_{f} + {\frac{a \cdot M_{f}}{L_{d}} \cdot {\overset{\sim}{V}}_{d}}} \leq V_{bat}$${{and} - \sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}}} \leq {{\overset{\sim}{V}}_{d} + {\frac{M_{f}}{L_{f}} \cdot {\overset{\sim}{V}}_{f}} - {\frac{M_{f}}{L_{f}} \cdot A_{f}}} \leq \sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}}$

which implies:

$\begin{matrix}{{{\frac{L_{d}}{a.M_{f}} \cdot \left( {{- V_{bat}}\mspace{14mu} - {\overset{\sim}{V}}_{f}} \right)} \leq {\overset{\sim}{V}}_{d} \leq {\frac{L_{d}}{a.M_{f}} \cdot \left( {V_{bat}\mspace{14mu} - {\overset{\sim}{V}}_{f}} \right)}}{and}} & \left( {{Eq}.\mspace{14mu} 6} \right) \\{{{{- \sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}}} - {\frac{M_{f}}{L_{f}} \cdot {\overset{\sim}{V}}_{f}} + {\frac{M_{f}}{L_{f}} \cdot A_{f}}} \leq {\overset{\sim}{V}}_{d}}{{\overset{\sim}{V}}_{d} \leq {\sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}} - {\frac{M_{f}}{L_{f}} \cdot {\overset{\sim}{V}}_{f}} + {\frac{M_{f}}{L_{f}} \cdot A_{f}}}}} & \left( {{Eq}.\mspace{14mu} 7} \right)\end{matrix}$

Thus, to ensure that there is a {tilde over (V)}_(d) that satisfiesequations 6 and 7 (Eq. 6), (Eq. 7), the following should apply:

${{- \sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}}} - {\frac{M_{f}}{L_{f}} \cdot {\overset{\sim}{V}}_{f}} + {\frac{M_{f}}{L_{f}} \cdot A_{f}}} \leq {\frac{L_{d}}{a.M_{f}} \cdot \left( {V_{bat}\mspace{14mu} - {\overset{\sim}{V}}_{f}} \right)}$and${\sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}} - {\frac{M_{f}}{L_{f}} \cdot {\overset{\sim}{V}}_{f}} + {\frac{M_{f}}{L_{f}} \cdot A_{f}}} \leq {\frac{L_{d}}{a.M_{f}} \cdot \left( {{- V_{bat}}\mspace{14mu} - {\overset{\sim}{V}}_{f}} \right)}$

The following inequality 8 (Eq. 8) is deduced therefrom:

$\begin{matrix}{{{{- \frac{1}{{L_{d} \cdot L_{f}} - {a \cdot M_{f}^{2}}}}\left( {{a \cdot M_{f} \cdot L_{f} \cdot \sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}}} + {a \cdot M_{f}^{2} \cdot A_{f}} + {L_{d} \cdot L_{f} \cdot V_{bat}}} \right)} \leq {\overset{\sim}{V}}_{f}}\mspace{20mu} {and}{{\overset{\sim}{V}}_{f} \leq {\frac{1}{{L_{d} \cdot L_{f}} - {a \cdot M_{f}^{2}}}\left( {{{a \cdot M_{f} \cdot L_{f}}\sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}}} - {a \cdot M_{f}^{2} \cdot A_{f}} + {L_{d} \cdot L_{f} \cdot V_{bat}}} \right)}}} & \left( {{Eq}.\mspace{14mu} 8} \right)\end{matrix}$

The controls obtained from the first transformation comprising thechange of variable of equation 2 can then be saturated by defining themaximum and minimum limits of the control signals {tilde over (V)}_(d),{tilde over (V)}_(d), {tilde over (V)}_(f):

$\mspace{20mu} {{{B\mspace{11mu} {min\_}{\overset{\sim}{V}}_{d}} \leq {\overset{\sim}{V}}_{d} \leq {B\mspace{11mu} {max\_}{\overset{\sim}{V}}_{d}}},\mspace{20mu} {with}}$${B\mspace{11mu} {min\_}{\overset{\sim}{V}}_{d}} = {\max\left( {{\frac{L_{d}}{\alpha \cdot M_{f}} \cdot \left( {{- V_{bat}}\mspace{14mu} - {\overset{\sim}{V}}_{f}} \right)},{{- \sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}}} - {\frac{M_{f}}{L_{f}} \cdot {\overset{\sim}{V}}_{f}} + {\frac{M_{f}}{L_{f}} \cdot A_{f}}}} \right)}$  and${B\mspace{11mu} {max\_}{\overset{\sim}{V}}_{d}} = {\min\left( {{\frac{L_{d}}{\alpha \cdot M_{f}} \cdot \left( {V_{bat}\mspace{14mu} - {\overset{\sim}{V}}_{f}} \right)},{\sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}} - {\frac{M_{f}}{L_{f}} \cdot {\overset{\sim}{V}}_{f}} + {\frac{M_{f}}{L_{f}} \cdot A_{f}}}} \right)}$$\mspace{20mu} {{{B\mspace{11mu} {min\_}\overset{\sim}{V_{q}}} \leq {\overset{\sim}{V}}_{q} \leq {B\mspace{11mu} {max\_}{\overset{\sim}{V}}_{q}}},\mspace{20mu} {with}}$$\mspace{20mu} {{B\mspace{11mu} {min\_}{\overset{\sim}{V}}_{q}} = {- \sqrt{\frac{V_{bat}^{2}}{3}}}}$  and$\mspace{20mu} {{B\mspace{11mu} {max\_}{\overset{\sim}{V}}_{q}} = \sqrt{\frac{V_{bat}^{2}}{3}}}$$\mspace{20mu} {{{B\mspace{11mu} {min\_}{\overset{\sim}{V}}_{f}} \leq {\overset{\sim}{V}}_{f} \leq {B\mspace{11mu} {max\_}{\overset{\sim}{V}}_{f}}},\mspace{20mu} {with}}$${B\mspace{11mu} {min\_}{\overset{\sim}{V}}_{f}} = {{- \frac{1}{{L_{d} \cdot L_{f}} - {a \cdot M_{f}^{2}}}} \cdot \left( {{a \cdot M_{f} \cdot L_{f} \cdot \sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}}} + {\alpha \cdot M_{f}^{2} \cdot A_{f}} + {L_{d} \cdot L_{f} \cdot V_{but}}} \right)}$  and${B\mspace{11mu} {max\_}{\overset{\sim}{V}}_{f}} = {\frac{1}{{L_{d} \cdot L_{f}} - {a \cdot M_{f}^{2}}} \cdot \left( {{a \cdot M_{f} \cdot L_{f} \cdot \sqrt{\frac{V_{bat}^{2}}{3} - {\overset{\sim}{V}}_{q}^{2}}} - {a \cdot M_{f}^{2} \cdot A_{f}} + {L_{d} \cdot L_{f} \cdot V_{bat}}} \right)}$

Then, the control signals {tilde over (V)}_(d), {tilde over (V)}_(q),{tilde over (V)}_(f) are saturated, that is to say that the controlsignals are clipped when these signals depart from the bands defined bythe maximum and minimum limits. For this, {tilde over (V)}_(q) is firstof all clipped, for which the limits depend only on the Vbat value, then{tilde over (V)}_(f) is clipped, for which the limits depend only on theVbat values and on the calculated saturated value of {tilde over(V)}_(q), and finally {tilde over (V)}_(d) for which the limits dependon the Vbat value and on the calculated saturated values of {tilde over(V)}_(q) and {tilde over (V)}_(f).

In other words, sat ({tilde over (V)}_(q)) is calculated according tothe following equation:

sat({tilde over (V)} _(q))={tilde over (V)} _(q), if B min_(—) {tildeover (V)} _(q) ≦{tilde over (V)} _(q) ≦B max_(—) {tilde over (V)} _(q)

sat({tilde over (V)} _(q))=B min_(—) {tilde over (V)} _(q), if {tildeover (V)} _(q) <B min_(—) {tilde over (V)} _(q)

sat({tilde over (V)} _(q))=B max_(—) {tilde over (V)} _(q), if {tildeover (V)} _(q) >B max_(—) {tilde over (V)} _(q)

by using Vbat

Then sat({tilde over (V)}_(f)) is calculated according to the followingequation:

sat({tilde over (V)} _(f))−{tilde over (V)} _(f), if B min_(—) {tildeover (V)} _(f) ≦{tilde over (V)} _(f) ≦B max_(—) {tilde over (V)} _(f)

sat({tilde over (V)} _(f))−B min_(—) {tilde over (V)} _(f), if {tildeover (V)} _(f) <B min_(—) {tilde over (V)} _(f)

sat({tilde over (V)} _(f))−B max_(—) {tilde over (V)} _(f), if {tildeover (V)} _(f) >B max_(—) {tilde over (V)} _(f)

by using the Vbat value and the calculated sat({tilde over (V)}_(q))value

Then sat({tilde over (V)}_(d)) is calculated according to the followingequation:

sat({tilde over (V)} _(d))−{tilde over (V)} _(d), if B min_(—) {tildeover (V)} _(d) ≦{tilde over (V)} _(d) ≦B max_(—) {tilde over (V)} _(d)

sat({tilde over (V)} _(d))−B min_(—) {tilde over (V)} _(d), if {tildeover (V)} _(d) <B min_(—) {tilde over (V)} _(d)

sat({tilde over (V)} _(d))−B max_(—) {tilde over (V)} _(d), if {tildeover (V)} _(d) >B max_(—) {tilde over (V)} _(d)

by using the Vbat value and the sat({tilde over (V)}_(q)) and sat({tildeover (V)}_(f)) values.

In step 1, in order to keep a total control of the currents, a blockingis imposed on the current setpoints I_(d) ^(ref), I_(q) ^(ref), I_(f)^(ref) to obtain the current setpoints V_(d) ^(ref)_sat, I_(q)^(ref)_sat and I_(f) ^(ref)_sat according to the following principle:

If {tilde over (V)}_(d) reaches its maximum limit B max_{tilde over(V)}_(d), the increasing of the setpoint is stopped at I_(d). Inpractice, according to equation 3 (Eq. 3), this would cause {tilde over(V)}_(d) to be increased even further. Similarly, the setpoint is notreduced at I_(q). Finally, the setpoint is not increased at I_(f). Inpractice, by blocking the increasing of the setpoint at I_(f), accordingto equation 3 (Eq. 3) an increase of {tilde over (V)}_(f) is avoidedwhich would reduce the maximum limit of {tilde over (V)}_(d) Bmax_{tilde over (V)}_(d) according to equations 6 and 7 (Eq. 6, Eq. V).

If {tilde over (V)}_(d) reaches its maximum limit B min_{tilde over(V)}_(d), the reducing of the setpoint is stopped at I_(d). In practice,according to equation 3 (Eq. 3), this would cause {tilde over (V)}_(d)to be reduced even further. Similarly, the setpoint is not increased atI_(q). Finally, the setpoint is not reduced at I_(f). In practice, thereducing of the setpoint at I_(f) would cause {tilde over (V)}_(f) to bereduced according to equation 3 (Eq. 3) and a consequential increase ofthe minimum limit of {tilde over (V)}_(d) B min_{tilde over (V)}_(d)according to equations 6 and 7 (Eq. 6, Eq. V).

If {tilde over (V)}_(q) reaches its maximum limit B max_{tilde over(V)}_(q), then no current setpoint should be increased further accordingto equation 3 (Eq. 3).

Similarly, if {tilde over (V)}_(q) reaches its minimum limit Bmin_{tilde over (V)}_(q), then no current setpoint should be reducedfurther.

Finally, if {tilde over (V)}_(f) reaches one of its limits B min_{tildeover (V)}_(f) or B max_{tilde over (V)}_(f), this phenomenon is onlytemporary because the axis f supports only low currents. This willtherefore create a dynamic saturation of the trend of the current in therotor but this does not pose any problem of stability. There is no needto saturate one of the current setpoints in this case.

Finally, in the step 4, there is a second transformation comprising achange of variable that is the reverse of the change of variable ofequation 2 (Eq. 2). In other words, the saturated control signalssat(V_(d)) , sat(V_(q)) , sat(V_(f)) are calculated in the Parkreference frame without a change of variable according to the saturatedcontrol signals sat({tilde over (V)}_(d)), sat({tilde over (V)}_(q)),sat({tilde over (V)}_(f)) by using the variable change equation 2 (Eq.2). The control signals sat(V_(d)), sat(V_(q)), sat(V_(f)) are thenapplied to the synchronous motor. More specifically, the signalssat(V_(d)), sat (V_(q)) are applied to the stator and the signalsat(V_(f)) is applied to the rotor.

The control method obtained is efficient from a point of view of thereliability and robustness with respect to disturbances. It allows for asaturation which does not disturb the dynamic decoupling of the changeof variable. The risks of racing and of loss of control of the motor arethus avoided.

FIG. 2 shows a control device comprising a means for blocking thecurrent setpoints 5 which applies the blocking of the currents describedin step 1 of the method. The blocking means also comprises a means foracquiring current setpoints, namely:

-   -   I_(d) ^(ref): the stator current setpoint on the axis d.    -   I_(q) ^(ref): the stator current setpoint on the axis q.    -   I_(f) ^(ref): the rotor current setpoint on the axis f.

The blocking means 5 comprises a means for receiving an indication INDICwhich indicates if one of the controls {tilde over (V)}_(d), {tilde over(V)}_(q), {tilde over (V)}_(f) has reached the minimum and maximumlimits defined in step 4 of the method. Based on this saturationindication the blocking means blocks the corresponding current setpointsI_(d) ^(ref) I_(q) ^(ref) I_(f) ^(ref) as is defined for step 1 of themethod.

The blocking means 5 is linked at the output to a means 6 for regulatingthe intensities of the rotor and of the stator I_(d), I_(q) and I_(f).For this, the regulation means 6 applies equation 5 (Eq. 5).

The control device is linked to sensors. The regulation means comprisesa means for processing the signals from the sensors and a dataacquisition means. The processing means is capable of filtering andscaling the signals received from the sensors.

Among the signals received from the sensors, there are the measurementsof the currents I_(d), I_(q) and I_(f) and, optionally, the valuesL_(d), L_(q), L_(f), R_(s), R_(f) and M_(f).

Among the data acquired by the acquisition means, there are the settingparameters K_(d), K_(g), K_(f), K_(id), K_(iq), K_(if).

The regulation means 6 is linked at the output to the saturation means7. The saturation means saturates the control signals {tilde over(V)}_(d), {tilde over (V)}_(q), {tilde over (V)}_(f) obtained from saidfirst transformation according to step 3 of the method to obtain thesignals sat({tilde over (V)}_(d)), sat({tilde over (V)}_(q)) andsat({tilde over (V)}_(f)).

The saturation means 7 is linked at the output to a transformation means8 capable of determining the signals sat(V_(d)), sat(V_(q)), sat(V_(f)),based on the transformed signals sat({tilde over (V)}_(d)), sat({tildeover (V)}_(q)) and sat({tilde over (V)}_(f)). For this, thetransformation means 8 applies equation 2 (Eq. 2). The control signalssat(V_(d)), sat(V_(q)), sat(V_(f)), are then applied to the synchronousmotor. More specifically, the signals sat(Vd), sat(V_(q)) are applied tothe stator and the signal sat(V_(f)) is applied to the rotor.

The saturation means 7 is configured to transmit to the blocking means 5the saturation indication INDIC. For this, it comprises means forcommunicating the information INDIC.

1-8. (canceled)
 9. A method for controlling a power train installed in amotor vehicle and including an electric motor including a rotor and astator, the method comprising: regulation of rotor and stator currentsvia control signals for the electric motor, the currents and the controlsignals being expressed in a revolving reference frame and including aplurality of axes, the control signals being derived from a firsttransformation including a change of variable allowing for dynamicdecoupling between the control signals along each of the axes of theplurality of axes; saturation of the control signals obtained from thefirst transformation to satisfy constraints associated with a batteryinstalled in the motor vehicle and connected to the electric motor; andblocking of at least some of regulation current setpoints if the controlsignals are saturated.
 10. The method as claimed in claim 9, furthercomprising a second transformation including a change of variable thatis reverse of the change of variable allowing for dynamic decoupling toexpress the control signals after saturation in the revolving referenceframe without a change of variable.
 11. The method as claimed in claim9, further comprising communication of information relating to thesaturation of the control signals, and wherein the blocking of theregulation current setpoints is performed based on the information. 12.The method as claimed in claim 9, wherein the reference frame in whichthe currents and the control signals are expressed is a Park referenceframe.
 13. A system for controlling a power train installed in a motorvehicle and including an electric motor including a rotor and a stator,the system comprising: means for regulating rotor and stator currentsusing control signals for the electric motor, the currents and thecontrol signals being expressed in a revolving reference frame andincluding a plurality of axes, the control signals being obtained from afirst transformation including a change of variable allowing for dynamicdecoupling of the control signals along each of the axes of theplurality of axes; means for saturating the control signals obtainedfrom the first transformation to satisfy constraints associated with abattery installed in the motor vehicle and connected to the electricmotor; and a blocking means configured to perform blocking of at leastsome of current setpoints of the regulation means if the control signalsare saturated.
 14. The system as claimed in claim 13, further comprisinga means for computing a second transformation including a change ofvariable that is reverse of the change of variable allowing for thedynamic decoupling to express the control signals after saturation inthe revolving reference frame without a change of variable.
 15. Thesystem as claimed in claim 13, further comprising means forcommunicating information relating to the saturation of the controlsignals, and wherein the blocking means blocks at least some of thecurrent setpoints of the regulation means based on the information. 16.The system as claimed in claim 13, wherein the revolving reference frameis a Park reference frame.